In today's information age, data communication networks are becoming more pervasive as an ever-increasing number of communication consumers require access to on-line computer resources. To that end, many data communication networks are evolving to meet the needs of these communication consumers. As these data communication networks evolve, it often becomes necessary to combine or integrate network segments that support different communication/transmission protocols.
One well-known communication protocol in widespread use is the X.25 protocol. The X.25 protocol defines the physical, link, and network layer protocols (layers one, two, and three) of the International Standards Organization ("ISO") seven-layer protocol model. In a communication network that utilizes the X.25 protocol (referred to herein as an "X.25 network"), two devices (referred to herein as an "X.25 device" or "X.25 devices") exchange X.25 data packets over a virtual circuit that is established across the X.25 network. One type of virtual circuit commonly used in the X.25 network is a permanent virtual circuit ("PVC"). A PVC is a virtual circuit that is set up automatically within the X.25 network and remains active as long as the X.25 network is operative. Unlike a PVC, a switched virtual circuit ("SVC") is set up only when explicitly requested by an X.25 device. Typical X.25 networks support both permanent and switched multiple virtual circuits. As is known in the art, a data message typically is encapsulated within an X.25 transmission envelope for transmission via the PVC or SVC.
Another well-known communication protocol in widespread use is the Transmission Control Protocol ("TCP"). TCP is a connection-oriented transport layer protocol that is generally used in conjunction with a connectionless network layer protocol known as the Internet Protocol ("IP"). In a communication network that utilizes the TCP protocol (referred to herein as a "TCP/IP network"), two devices (referred to herein as a "TCP device" or "TCP devices") exchange TCP data segments over a TCP connection that is established across the TCP/IP network. In order to set up the TCP connection within the TCP/IP network, one TCP device transmits a specially formatted message (referred to herein as a "TCP SYN message") that includes, among other things, an IP address identifying the destination TCP device and a TCP port number identifying one of a number of applications supported by the destination TCP device. The combination of IP address and TCP port number is referred to herein as a "socket." Because the TCP connection is set up only when explicitly requested by a TCP device, the TCP connection is considered to be a switched connection and thus, is not considered to be a permanent connection. As is known in the art, a message is transmitted via the TCP protocol by means of a TCP segment.
Because both the X.25 protocol and the TCP protocol are in widespread use, it has become desirable for X.25 devices to communicate with TCP devices in certain data communication networks. Undesirably, the X.25 protocol is sufficiently different from the TCP protocol that X.25 devices cannot inherently communicate with TCP devices.